The first thing Adrià Plana, a dermatology specialist at Germans Trias Hospital, makes clear about the frequency with which children should shower is that scientific evidence is scarce. Studies on bathing practices, he points out, are very complex to conduct, which is why, often, "the recommendations we make as dermatologists and pediatricians are based more on theoretical assumptions and our cultural heritage than on firm scientific evidence." Broadly speaking, he adds, what we could say is that bathing cleanses, eliminates microorganisms from the skin, and also eliminates some of the fatty acids found in the skin and hair. This, the dermatologist warns, causes the skin "to have a lower bacterial load and be cleaner, but it also causes the skin to dry out because there is an increase in transepidermal water loss."